Rule: A noun preceding an -ing participle head is normally understood as the direct object of the underlying verb.
Examples of errors:
(1) Kassel studying is like shopping.
(2) There is a big difference between baby learning and the learning of older people.
Although the traditional grammatical term for -ing forms used as nouns is "gerund", for the sake of simplicity the term "participle" refers here to the gerund as well as to what is traditionally called the present participle. When the -ing participle functions as the head of a noun phrase, and is modified by a preceding noun, two basic types can be distinguished, depending on the underlying relationship of the preceding noun modifier to the head. In the first, and most productive, category, the premodifying noun is the underlying direct object of the verb:
lion hunting <- the hunting of lions <- (someone) hunt lions
language learning <- the learning of languages <- (someone) learn languages
In the second, less productive, category the preceding noun, has an underlying adverbial relationship of place, time, or manner) to the head noun:
city driving <- driving in the city <- (someone) drive in the city
fist fighting <- fighting with (one's) fists <- (someone) fight with his fists
night driving <- driving at night <-(someone) drive at night
Kassel studying (cf. (1)) could, theoretically, mean either 'the study of Kassel as a subject' or 'studying in Kassel'. Why is it, then, that only the first interpretation--which is not the one intended by the author--is possible? There seems to be a restriction, in such ambiguous cases, which allows only the interpretation corresponding to the most productive structure (i.e. underlying verb + object relation). This restriction does not apply if the ambiguity is removed by substituting lexical items that allow only one logical interpretation, as in
Kassel driving can be hectic, particularly at rush hour.
Here 'driving in Kassel' (not 'the driving of Kassel') is the only logically possible interpretation.
Rule 1.9.1 also accounts for the unacceptability of (2), since it is quite uncommon for the preceding noun to represent the subject of the underlying verb, which would be the case here (but cf. Dog barking is irritating). Adult learning is acceptable because adult here is an adjective, but grown-ups learning would not be acceptable.